The primary objectives of this research project are to establish and characterize a bona fide strain of human urothelial cells and to induce mutations to thioguanine resistance and to morphological transformation in vitro in these cells using chemical carcinogens and other mutagenic treatments, such as UV light. Cultures of normal human transitional epithelial cells will be initiated using explants of embryonic bladder and of postnatal ureter and bladder obtained from surgery. Several different culture media will be tested to determine which media best support the growth and the maintenance of normal human urothelial cells in culture. The morphological and growth characteristics of cells grown from primary explants will be studied at each stage of adaptation to tissue culture to determine (1) whether the cells cultured are truly urothelial cells and (2) whether the cell strains derived have useful in vitro growth parameters. Several epithelioid cell strains have already been derived from urothelial explants and one of these has been successfully used for quantitative mutation experiments. We are in the process of completing the characterization of these cell strains and we plan to use them in several preliminary transformation assays.